1. Field of Invention
The invention relates to a system and a protecting device thereof and in particular, to a fan system and a protecting device thereof capable of protecting a motor from damage.
2. Related Art
Referring to FIGS. 1 and 2, a conventional fan system 1 includes a driving device 11, a switch device 12 and a fan motor 13. FIG. 2 shows an equivalent circuit diagram of the fan system 1. The driving device 11 generates a first input signal S1 and a second input signal S2. The first input signal S1 is a pulse signal and can be converted into an inverse pulse signal, which is the second input signal S2, by a switch element 1111 of a phase inverter 111. Accordingly, the second input signal S2 and the first input signal S1 have opposite phases. In addition, the driving device 11 may be a Hall effect IC, and the first input signal S1 and/or the second input signal S2 may be Hall signals. The switch device 12 has two switch elements 121 and 122 for receiving the first and second input signals S1, S2, respectively. The motor 13 has a first coil 131, a second coil 132 and a rotor (not shown). In this example, the motor 13 is a DC brushless motor. The driving device 11 is electrically connected with the switch device 12, and the switch elements 121 and 122 of the switch device 12 are electrically connected with the first hand second coils 131, 132 of the motor 13, respectively. As shown in FIG. 2, the fan system 1 operates as follows. The driving device 11 controls the switch elements 121 and 122 to turn on through the first and second input signals S1, S2, respectively, to alternately drive the first and second coils 131, 132 to produce the electromagnetic induction with the rotor and to make the motor 13 rotate.
When the fan system 1 is influenced by external forces or the internal element is loosened to jam and stop the rotor, the first input signal S1 or the second input signal S2 turns into a high-potential signal.
Because the fan system 1 cannot judge that the motor 13 has stopped rotating, the motor 13 continuously receives the first input signal S1 and the second input signal S2. However, the electric energy received by the motor 13 cannot be converted into the kinetic energy, which is to be released, through the rotor, but is converted into heat to rise the temperature of the motor 13. Thus, the motor 13 may be damaged or burn out due to the overheating, and the reliability and the lifetime of the motor 13 are thus decreased.
Therefore, it is an important subject to provide a fan system and its protecting device capable of protecting the motor from damage when the motor gets abnormal or stops.